StarkWare, the team that pioneered zero-knowledge-based rollups in 2018 and has been instrumental to scaling Ethereum through its Layer 2 Starknet, has unveiled an ambitious plan to now scale Bitcoin.

“We want to seize the moment,” StarkWare’s Co-founder and CEO Eli Ben-Sasson told The Defiant. “In the time since the Taproot upgrade, research has helped us to appreciate that it has unlocked pathways to new possibilities over BTC.”

Taproot, which was implemented November 2021, was the latest and largest of Bitcoin’s upgrades. It seeks to boost smart contracts and privacy to Layer 1 transactions, a much-needed feature for the network. But according to a dashboard by Bitcoin core contributor Luke Dash Jr., barely 12% of Bitcoin nodes are running an upgraded Taproot version of the software.

Nonetheless, Ben-Sasson is gearing to make the most of the latest improvement.

The team has allocated a $1 million fund for research and development to make StarkWare’s Bitcoin scaling plan possible. Funds will go to researchers specifically dedicated to gaining a deeper understanding of OP_CAT, a Satoshi-era script of Bitcoin that has now resurfaced.

A Controversial Revival

OP_CAT, short for “Operation Concatenate,” is an opcode that was initially proposed by Bitcoin’s creator, Satoshi Nakamoto. The opcode allows for the combination of two pieces of data into a single piece of data during the execution of a Bitcoin transaction.

Essentially, OP_CAT enables specific features that can limit or expand how bitcoin can be transacted in the future. Use-cases include secure vaults that would allow reversible transactions, automated recurring payments, or time-locked transfers for inheritance schemes.

But Satoshi Nakamoto actually removed OP_CAT in 2011, citing concerns that it would expose the network to security issues, such as denial-of-service (DoS) attacks if used in conjunction with other similar scripts.

According to Ben-Sasson, the probability of OP_CAT being adopted is high, which places StarkWare’s plan in an exciting position. “It will retain all Bitcoin values unchanged,” he explained, “while providing a bare bones framework that is just enough to bring STARK scaling to Bitcoin.

Reactivating OP_CAT has its defenders along with detractors.

Udi Wertheimer, well-known Bitcoin troll and Co-founder of the Taproot Wizards, has been touting the script since it was introduced back in October 2022. He has claimed that OP_CAT will allow scaling without changing the core fundamentals of Bitcoin–a sentiment shared by Ben-Sasson.

Others aren’t so sure about that.

Detractors Call It An Attack

Robin Linus, the creator of BitVM, a proposed system that allows complex computations and smart contracts to be executed on the Bitcoin network, previously said that OP_CAT “fundamentally changes Bitcoin’s nature, introducing a new attack surface that nobody fully comprehends.”

Notably, Ben-Sasson told The Defiant that one of the teams they were working with to get StarkWare’s ambitious plan off the ground is BitVM.

Others agree with Linus, although in slightly different fashion.

As Matt Corrallo, a Bitcoin core contributor explained in an April 16 post titled “Stop Calling It MEV,” systems that have arbitrarily expressible smart contracts are likely to have the potential for advanced MEV extraction similar to what we see on Ethereum today.

Implementing OP_CAT opens the door to that possibility.

Corrallo didn’t explicitly state he was against OP_CAT, but his points were taken by bitcoiners that are against the upgrade. Others also called out the inability of OP_CAT defenders to voice risks that come with reviving and reimplementing the script.

The pseudonymous technical editor for Bitcoin Magazine Shinobi wrote on X on March 14 that the “If we don’t know the limits of what this can do or the potential effects it could have, adding it into Bitcoin sounds like a horrible idea, imo.”

An Ambitious Plan

That said, Ben-Sasson’s team isn’t shying away from its plan. He also outlined his general vision early this Tuesday morning in a video post.

StarkWare is the team behind StarkNet, one of the top scaling solutions for Ethereum which currently holds $294 million in Total Value Locked (TVL), according to DeFiLlama. The team is now intent on taking that success, and replicating it on Bitcoin.

To scale Ethereum–and now hopefully Bitcoin–StarkWare uses zero-knowledge rollups. These use the minimal amount of information needed to verify a transaction, reducing the data load on the network.

Rollups have been largely touted by the teams developing them as the answer to scaling woes suffered by blockchains. They do not trade off security, but rather inherit the protections of Layer 1s, while allowing for faster and more transactions to happen off chain.

These could be the right answer for the Bitcoin ecosystem, well known for its slow transaction throughput and high fees when congested. However, the solution delivered here with OP_CAT is a contentious option, and one that might get pushback from the overall Bitcoin community.

As OP_CAT continues to get tested on Bitcoin’s testnet–it was launched in early April 2024–the task at hand will be to see if the overall community is up for reviving its ten lines of code.